The present invention relates to managing freezer operations as a function of off-peak energy demand periods.
A freezer typically includes a thermally insulated compartment that maintains subfreezing air. Some freezers are attached to a refrigerator while other freezers are freestanding. Many freezers permit a consumer to set an internal air temperature of the freezer to between xe2x88x9220 degrees and 20 degrees Fahrenheit (F.) (xe2x88x9229 degrees to xe2x88x927 degrees Celsius (C.)). To rapidly freeze and store food items and to save energy, most consumers maintain the freezer air temperature at around zero degrees F. (xe2x88x9218 degrees C.).
In contrast to a refrigerator, a freezer typically has only one energy-using device: a compressor. A thermomechanic device such as a thermostat typically controls the on/off operations of the compressor to create and maintain subfreezing air. When energized, the compressor is used to draw out heat from the interior of the freezer. However, freezers require a significant amount of energy to create subfreezing air.
The energy costs to create subfreezing air in a freezer may depend upon the time of day. In areas of the United States where energy is at a premium, utility companies often divide their rates into off-peak and on-peak energy rates based on off-peak and on-peak energy demand periods. Energy used during off-peak may cost the consumer in United States dollars around 2¢ to 3¢ per kilowatt-hour (kWh) while on-peak energy may cost anywhere from 6¢ per kWh to 50¢ or more per kWh. The utility companies eventually pass these extra costs to the consumer. In a recent California energy crisis, the wholesale cost of energy rose to $3.00 per kWh.
Without some sort of management, a freezer that creates subfreezing air based on the demand of a household most likely will operate when energy demand on a utility company is at its highest. Drawing power to create subfreezing air during these on-peak periods increases a consumer""s monthly energy bill. In the collective, this lack of demand side management places excessive wear on a power plant to shorten the overall life of the plant.
Many utility companies have off-peak energy usage programs that provide lower energy rates. These lower energy rates apply so long as the consumer""s appliance draws power only during off-peak times. Off-peak energy usage programs typically aid in reducing on-peak demand. However, there may be times during the on-peak periods when the temperature of the consumer""s freezer is above levels at which food may be stored safely. Here, the consumer may override the clock timer to bring the temperature within safety levels but will incur significant kWh energy charges. What is needed is a system that manages the creation of subfreezing air in a freezer during the off-peak periods to supply needs of a consumer during the on-peak periods, to time shift consumer demands on power plants, and to save the consumer money.
In light of the above noted problems, the invention works towards providing a system that creates subfreezing temperatures in a freezer during the off-peak periods. During the off-peak periods, the freezer system invention may subfreeze the interior temperature in a freezer to very low temperatures that may last throughout a normal day""s use of the freezer, including during the on-peak periods. Since the freezer subfreezes during off-peak periods, consumer demands on power plants may be shifted away from on peak periods and the consumer may save money.
Thus, in a preferred embodiment, the invention provides a freezer system having a freezer, a thermoelectric device, and a controller. The freezer may include a compressor and a compartment, where the compartment may store subfreezing air. The thermoelectric device may be a temperature sensor positioned in thermal communication with the compartment. The controller may be coupled to the compressor and the thermoelectric device. The controller is configured to deliver power to the compressor based on a temperature signal and a control signal. The temperature signal may be from the thermoelectric device and the control signal may be selected from an off/on peak signal and an override signal.
These and other objects, features, and advantages of the present invention will become apparent upon a reading of the detailed description and a review of the accompanying drawings. Specific embodiments of the present invention are described herein. The present invention is not intended to be limited to only these embodiments. Changes and modifications can be made to the described embodiments and yet fall within the scope of the present invention.